Lock-joint metal tubing



Patented July 2, 1929.

UNITED: STATES 5 PATIENT; OFFICE.

mam: w. SCHNEIBLE, or noun, new Yoax, assumes 3150 norm iranurac'ruame I comrm, or none, nnw YORK, A conrona'rroiv.

. LocxJoInr METAL: 'runina.

Application filed December 6, 1926. Serialj o'.. 152 888.

My presentinvention relates to lock joint metal tubing. 1 e

The subject-matter of this application was originally a part of an application filed by 6' meAugust 10, 1925,as Serial'Number 4 9539.

In lock-joint metal tubing the oppos te edges of a strip of sheet. metal are formed into hooks, thestrip of metal is bent into a more or less circular form andjthese hooks 10 brought into engagement with each other and then closed down upon each other to] a complete the. tubing. Whilethis lock-joint does not pull apart thejoint s not and especially under strain or after fabrication does not remain rigid; for instance when a,

length of it is subjectedto a twisting strain the tube will twist through tlieinterengagf ing hooks sliding slightly on each other; and this slidingis especially noticeable after the tubing has been subjected to a bending or other fabricating operation as when a length of it has been bent to form a head or footj frame of a bedstead. This slipping of the joint results in the e pp p 2 therefrom" not having the rigidity which should be resent in a really solid piee'eof tubing. T e purpose of my invent on is overcome the above faultinlockqoint tubing and to provide lock-joint tubing which 1s rigid both in the original tubing and which stays rigid or non-slipping n its oint even after the tubing has been sub ec ted to a bending or other fabricating operation or operation-s. I accomplish this by knurlingor otherwise roughening the faces or certain of the faces adjacent t e opposite edges of the strip of metal that are Further urposes and advantages ofmy invention wi lappear from the specifications and claims herein.

Figs. 1 and 2 are plan views respectively of the outside facefland of the inside face of ashort length of a strip of sheet metal as knurled preparatory to being formed into lock-joint tu ing pursuant tomy invention.

Fig. 3 is a sectional view on line 3-3 of Fig. 2.

Fig. 4 is a sectional view similar to Fig. but on an enlarged scale.

Fig. 5 is a similar sectional view through the strip after it has had the'hooks formed in its edges andhas been rolled to be U-shaped incross section. o o

.ment but tubing or the article made to interengage in the lock- Fig. '6 is a similar sectional view after the hooked edge upon each other.

' Fig. 7 is a similar sectional? view through the completed tubing.

Figs. 8, and 10are detailed sectional views on a greatly enlarged. scale through the hooked edges as they appear in Figs. 5, 6 and 7 respectively. o

Figs. 11, 12. and 13 are detailed sectional views on a greatly enlarged scale through the hooked edges. of tubing embodying various modifications of my invention.

In the drawings I'have shown a lock-joint metal tubing embodying several forms of m invention but it will be understood that such drawings are illustrative of my invention and s have been brought into engagea efore the hooks have been closed that as indicated in the claimsherein, my

in the drawings and described in detail in the specification.

strip of sheet metal from which the tubing X is to be formed has one or both of its surfaces I Referring to the drawings in amore par- *iticular description it will be seen that the outside face and a similar relatively narrow band 12 onits inside face knurled or otherwise roughened, while at the edge B of the metal only the outside or outer face of the metal is knurled as at the relatively wider band 13. Under this arrangement the edge A of the strip of metal is subsequently formed into what I will call for definiteness the inner hook and the edge B of the stri of metal will beformed into what I will call for definiteness the outer hook. An-inspection of the drawings will then show that the inner book has on its opposite faces the knurled bands 11 and 12 and that the relatively wider knurled band 13 formed on the into the outer hook has its knurled band 13 .edge B when said edge B has been formed disposed partly upon the inwardly facin side of the portion 14 of this outer hook an partly upon the outwardly facing side of the portion 15 of this hook. e

As the strip of metal is progressed through the machine the hooks will be brought into the position shown in Figs. 7 andlO.

inspection of the larger views Figs. 9 and 10 will show that the portion of the knurled band 13 on the part 14 of the outer hook will into the permanent position shown in Fig.' 10, it would be obvious that these two pairs of oppositely disposed knurled faces will be brought into intimate or very tight contact. The effect of the knurling or rou-ghenin of these knurled bands of metal is to pro uce small rid es of metal extending up from the 7 general ace of the material usually upon both sides of the slight depressions formed by the knnrlingirol s or. other mechanism used 'to roughen or knurl the-metal. These minute outstanding ridges especially in ,conjunction with the depressions will, when the lock-joint is pressed tightly together, form a lock-joint which will not slip when .a len th of tubmg is subjected to a twisting action and so will neutralize or greatly reduce any tendency of the tubing to twist for the reason that edges in the lock-joint can not now slip on each other; for the same reason the knurled surfaces will hold the twoparts of the lock-'oint permanently in position even though t e tubing be subjected to bending or other fabricating operations.

In Figs. 1 to 10 I have shown m invention as utilizing two pairs of opposite y disposed knurled faces interengaging within the lockjoint. This construction I believe to be the preferred embodiment of my invention.- In Fig. 11 I have shown a construction wherein on yone pair or interengagin knurled surfaces are used, namely, at theband 11 on the inner hook and at the band 16 on the outer hook upon the outwardly facing surface of the portion 15 of this hook.

It will be obvious that any other .interengaging pair of surfaces might be knurled. It will also be obvious that the knurling or rougheningmay be upon three pairs of interengaging surfaces as shown in Fig. 12. This example of my construction variesfrom that shown in Figs. 1 to 10 in that there'isa band of knurling at- 17 upon the main body of the tube material adjacent the inner hook and a co-operating band as at 18 upon the outwardly facing surface of the portion 14 of the inner hook. It is believed, however, that the addition of this last air of knurled surfaces is not necessary in or er to effect a good non-slipping joint.

In Fig. 13 I h'ave shown a construction where all the'knurling is upon one part or edge of the tubing,.say on edge A but it might be all upon the other part. This construction .i s'within the broad scope of my invention'and is a;modification't'hat is available for certain'uses oftubing.

In all the forms of tubing embodying my invention it will be IIIIdGIStOOdZthfitthG knurling is slight ors hallow and does .not extend into the sheet metal suiiiciently to formser- :rations, knurling or unevenness on the other side of the material. :It will .be noted espec'ially that the knur'ling is never placed on a surface that will be exposed when the tubing .iscompleted. Consequently in the completed tube boththe exposed su rfaces,'viz ;the inside and the outsidesurfaces ofthe tubing at the oint will be smooth or free from serrations What Iclaim as new and desire to-secure by Letters Patent is:

1. Lock-joint metal tubing comprising a main tubularmember having .its edges provided with reversely disposed, turned-back hooked portions. inter-engaging each other and pressed together and to the co-operatmg.

portions at each edge opposite the hook portions, said hooked 'POItlOIIS and the portions of the tubing opposite said hooked portions each extending inan uninterrupted plane longitudinally of the seam with the inter-engagmg pairs of surfaces of saidhooked portlons within the 'joint'minutely knurled with serrations extending transversely of the joint I whereby longitudinal slippage of said edges relative to each other is prevented.

2. Lock-joint .meta'l tubing comprising a main tubular member having its edges provided with reversely disposed, turned-back hooked portions, iITter-engagingeach other and pressed together and to the co-operating .portionsat each edge-opposite the hook portions, said hooked portions and the portions of the tubing opposite said hooked portions each extending in an uninterrupted lane longitudinally of the seam with certaln of the inter-engaging pairs of surfaces of said hooked portions within the joint'minutely knurledwith serrations extending transversely of the 1' oint whereby longitudmal slippage of said edges relative to each other is prevented.

3. Lock-joint metal tubing comprising a main tubular member having its edges provided with reversely disposed, turned-back hooked portions, interengaging each other and pressed together and to theco-operating portions. at each edge opposite the hook portions, said hooked portions and the portions of the tubing opposite said hooked portions each extending in an uninterrupted plane longitudinally of the seam with the interengaging pa1rs .of surfaces of said hooked portions and co-operating opposite portions within the joint minutely knurled with serrations extending transversely of the f joint whereby longitudinal slippage of said edgeslrelative to eachrother is prevented.

4. Lock-joint metal tubing oom rising a main tubular member having its edges provided with reversely disposed, turned-back hooked portions; inter-engaging each other and pressed to ether and to the co-operating I main tubular member having its e ges ro-- other is portions within the joint; minutely knurled with serrations extending transverselyot thejoint whereby longitudinal slippage'o! said edges relative to each other is prevented. '5. Lock-'oint metal tubing comprising amain tubu ar member having its e ges provided with re'versely disposed, turned-back hooked portions, intenengagmg each other and pressed together and to the co-operate ing portionsat each edge opposite the hook portions, said hooked portions and. the pot-,

tions of the tubingopposite said hooked portions each extending. in an uninterrupted plane longitudinally of the seam with certain of the inter-engaging pairs of surfacesof said hooked portions and co-operatin opposite portions within the joint minute y knurled with nonv registerin g serrations extendin transversely of the oint whereby longitudinal slippage of sai edges relative to each revented. p. 6. Loc joint metal tubing com llSlIlg a vided with reversely disposed, turnedack hooked portions,iinter-engaging each other portions at ea of the tubing opposite said hooked portions each extending in an uninterrupted plane and ressed to ether and to the P cl; edge opposite the hook tions, said hooked port1ons and the portions longitudinally of the seam with certain of the .5

inter-engaging pairs of surfaces of said hooked portions'and co-operating1 opposite portions within the joint roug ened by minute non-re 'stering knurlings extending transverselyo the joint.

i 7. As a new article of manufacture lock- I joint metal tubin having atthe 'joint two inter-engaging1 hoo ed portions, the mass of each of em to being in an uninterrupted plane longitudinally o engaging surfaces of'said booked and cooperating parts within the joint minutely knurled. I p

8. Lock-"oint metal tubing'consisting of a main tubu or member having its edges ro- Hvided with reversely disposed, turnedack; hookedvportions, inter-engaging each other 1 and pressed to'gether and to the (o-operating 05- portions at each edge opposite the hook portions, said hooked portions and theportions of thetubing opposite said hooked portions each extending in an uninterrupted plane .lon'gicertain of thesur-Q 70 rtionswithinthe joint y tudinallv of the seam with faces of said hooked p0 ooked portions and of each ad-H jacent portion of each edge opposite there- 55 theseamv with certain of the interminutely knurled with serrations extendin transversely of the nal slippage of sai other is prevented. a r v In .witlnessggwhleaeof Iflppve afixedbe 1m signaturetis n so ovem r i IF A .w. ome 

